The first use of iron occurs in this period, complementing the older bronze working technology. The rearing of livestock seems to have been particularly important at this time when we see the development of tribes controlling particular areas of Britain. The most easily recognisable site of this period is the hillfort, a defended village and stronghold and in some places the centre for metalworking and other crafts. On lower ground farmsteads defended with banks and ditches topped by timber fences (palisades), in the manner of hillforts, were also occupied. Some people refer to Britain at this time as Celtic Britain and to the people as Celts.